Accurate preoperative localization remains the major determinant of successful surgery in the Zollinger-Ellison syndrome. In spite of multiple diagnostic modalities including selective arteriography, portal venous sampling, CT, MRI, and ultrasound (both pre and intraoperative), localization is achieved in only 60% of patients. The most successful preoperative localizing technique, portal venous sampling, is both invasive and technically demanding. We will add selective intraarterial injection of secretion to our routine preoperative anteriographic study to evaluate this technique with the hope that a positive test would eliminate the need for portal venous sampling.